Pneumatic tire having protrusion formed on sidewall

Abstract

A pneumatic tire includes a tread portion, a pair of sidewall portions, a pair of bead portions, and a protrusion. The protrusion includes a plurality of longitudinal ribs and a low height part. Each rib has a protruding height of 0.5 to 7.0 mm from the normal outer surface of the sidewall. Each low height part has a protruding height from the normal outer surface of the sidewall that is lower than that of the longitudinal ribs. The sidewall portion with the protrusion has a ratio between a total area of the protrusion projected onto the normal outer surface of the sidewall portion and an area between an outer circumferential line on the sidewall portion passing through a radially outmost point of the protrusion and an inner circumferential line on the sidewall portion passing through a radially innermost point of the protrusion in a range of from 50 to 80%.

What is claimed is: 
     
       1. A pneumatic tire comprising
 a tread portion, 
 a pair of sidewall portions each extending radially inwardly from an edge of the tread portion, 
 a pair of bead portions each being formed on radially inner portion of the sidewall portion, 
 a protrusion being formed on at least one sidewall portion and protruding from a normal outer surface of the sidewall portion, wherein 
 the protrusion comprises 
 a plurality of longitudinal ribs each extending at angle of from 0 to 20 degrees with respect to a radial direction of the tire and 
 a low height part disposed between the longitudinal ribs, 
 each longitudinal rib has a protruding height of 0.5 to 7.0 mm from the normal outer surface of the sidewall portion, wherein the longitudinal rib comprises an outer wall surface extending radially inwardly from a radially outmost point of the rib while gradually increasing its protruding height, 
 each low height part has a protruding height from the normal outer surface of the sidewall which is lower than a maximum protruding height of the longitudinal ribs, wherein the low height part comprises a radially outer portion protruding beyond the outer wall surface of the longitudinal rib in a cross section view of the tire, and 
 the sidewall portion with the protrusion has a ratio A 1 /A 2  between a total area A 1  of the protrusion projected onto the normal outer surface of the sidewall portion and an area A 2  between an outer circumferential line on the sidewall portion passing a radially outmost point of the protrusion and an inner circumferential line on the sidewall portion passing a radially innermost point of the protrusion is in a range of from 50 to 80%. 
 
     
     
       2. The pneumatic tire according to  claim 1 , wherein
 the radially outmost point of the longitudinal rib is located in a range of from 0.5 to 0.85 times a tire section height from a bead base line, and 
 the radially innermost point of the longitudinal rib is located in a range of from 0.45 to 0.75 times the tire section height from the bead base line. 
 
     
     
       3. The pneumatic tire according to  claim 2 , wherein
 in the sidewall portion with the protrusion, a ratio A 1   o /A 2   o  is larger than a ratio A 1   i /A 2   i:    
 here, A 2   o  is an area between the outer circumferential line and a middle circumferential line which passes through the center point between the outer circumferential line and the inner circumferential line; 
 A 1   o  is an area of the protrusion formed in the area A 2   o;    
 A 2   i  is an area between the inner circumferential line and the middle circumferential line; and 
 A 1   i  is an area of the protrusion formed in the area A 2   i.    
 
     
     
       4. The pneumatic tire according to  claim 1 , wherein
 in the sidewall portion with the protrusion, a ratio A 1   o /A 2   o  is larger than a ratio A 1   i /A 2   i:    
 here, A 2   o  is an area between the outer circumferential line and a middle circumferential line which passes the center point between the outer circumferential line and the inner circumferential line; 
 A 1   o  is an area of the protrusion formed in the area A 2   o;    
 A 2   i  is an area between the inner circumferential line and the middle circumferential line; and 
 A 1   i  is an area of the protrusion formed in the area A 2   i.    
 
     
     
       5. The pneumatic tire according to  claim 1 , wherein
 the protrusion comprises a plurality of protrusion design units arranged repeatedly in the circumferential direction of the tire, and 
 the protrusion design units have a plurality of kinds with different pattern pitch of circumferential length of the tire. 
 
     
     
       6. The pneumatic tire according to  claim 5 , wherein
 a tread pattern of the tread portion is formed by tread design units arranged repeatedly in circumferential direction of the tire, 
 the tread design units have a plurality of kinds with different pattern pitch of circumferential length of the tire, and 
 each pattern pitch of the tread design units corresponds to each pattern pitch of the protrusion design units. 
 
     
     
       7. The pneumatic tire according to  claim 1 , wherein
 the tread portion is provided with a shoulder lug groove, 
 the shoulder lug groove extends from the tread portion beyond one of the tread edges and terminates without reaching the protrusion, 
 a circumferentially extending rib is provided between the shoulder lug groove and the protrusion, and 
 the circumferentially extending rib protrudes from the normal outer surface of the sidewall portion. 
 
     
     
       8. The pneumatic tire according to  claim 1 , wherein the outer wall surface of the longitudinal rib has a circumferential width which gradually decreases radially inwardly.